1. Field of the Invention
The present invention relates to an apparatus for applying a coating material intermittently to a surface of a substrate which is conveyed continuously.
2. Description of the Related Art
FIG. 4 shows a conventional intermittent coating apparatus. A coating die 1 is provided with a inlet port 3, a manifold chamber 4, a supply passage 5, and a discharge opening 7 defined by lips 6. A coating material 2 supplied through the inlet port 3 into the manifold chamber 4 in which the coating material 2 is stored temporarily The coating material 2 is supplied through the inlet passage 5 (as shown by arrows) and is extruded through the discharge opening 7 onto a surface of a substrate 8 being moved upward continuously at a uniform rate, as viewed in FIG. 4. A flexible sheet 9 similar to a diaphragm is placed in a draw-in chamber 14 formed in a part of the supply passage 5. The lower end of an operating rod 10 attached to the flexible sheet 9 is set upright and is biased upward by a spring 11. A cam follower 12 is supported for rotation in the upper end of the operating rod 10. An eccentric cam 13 which drives the operating rod 10 for reciprocating movement in the axial direction is in engagement with the cam follower 12. The eccentric cam 13 drives tho operating rod 10 up and down to bend the flexible plate 9 reciprocally. When the operating rod 10 is moved upward away from the supply passage 5, the flexible sheet 9 is force to bend in an upward convex shape with the volume of the draw-in chamber 14 increasing. Consequently, the amount of the-coating material 2 supplied while the flexible sheet 9 is bent in an upward convex shape is absorbed by the increase of the volume of the draw-in chamber 14 and the discharge of the coating material 2 onto the substrate 8 is suspended. Thus, the flexible sheet 9 is bent reciprocally in an upward convex shape to apply the coating material 2 intermittently to the substrate 8.
There are various patterns to intermittent coating on to the substrate 8 which has different pitch of the coating. The coating pattern is depend on the shape of the eccentric cam 13 which prescribes a cam diagram. It has a disadvantage that the eccentric cam 13 is unable to cope with the change of the coating material and the coating pattern. Therefore, a new eccentric cam must be newly designed and made when the coating material or the coating pattern is changed. However, the design of a suitable eccentric cam is difficult, and experiments must be conducted repeatedly by a trial-and-error method to design a suitable eccentric cam, which requires enormous time and expenses. The flexible sheet can be vertically deformed in a fixed range, and the circumference and the diameter of the eccentric cam must meet limiting conditions.
Accordingly, it is an object of the present invention to make making an eccentric cam every time the coating pattern or the coating material is changed unnecessary, to eliminate troublesome work requiring time and expenses for making an eccentric cam and to provide an intermittent coating apparatus capable of readily coping with the change of the coating material and coating conditions and of properly achieving a desired intermittent coating operation.
The present invention provides an coating apparatus for applying a coating material to a surface of a substrate beingmoved continuously, said apparatus comprises: a coating die provided with a inlet port through which the coating material is introduced into the coating die, a discharge opening confronting with the substrate, through which the coating material is discharged onto the surface of the substrate a supply passage defined in the coating die so as to communicate the inlet port with the discharge opening, a manifold chamber for temporarily storing the coating material supplied thereto and is formed in a part of the supply passage, and a flexible sheet adapted to be displaceable away from the supply passage so that a draw-in chamber for absorbing the coating material is formed in the supply passage, a ball screw mechanism having a ball screw adapted to move in the axial direction to cause the flexible sheet for displacement, a servomotor for driving the ball screw mechanism, and a intermittent motion generating means for applying an intermittent reciprocating motion to the ball screw so that the draw-in chamber repeats a expansion and a contraction periodically.
According to the present invention, it is unnecessary to prepare an eccentric cam every time the coating pattern or the coating material is changed, and troublesome work requiring time and expenses for conducting experiments and making eccentric cams by a trial-and-error method is eliminated. The present invention enables properly intermittently applying a coating material to a base sheet regardless of change in the coating pattern and/or the quality of the coating material.